1. Field of the Invention
The present invention relates to devices for driving flashes for photographing used in a camera, etc., and more particularly to a device for driving a light emitting diode (LED) for a flash of a camera, such as a digital camera or a small-size camera of a mobile phone, which is capable of driving the LED in two modes to reduce power consumption.
2. Description of the Related Art
With the popularization of digital cameras, recently, various mobile communication terminals, including mobile phones, have been marketed with small-size digital cameras contained therein. Flashes are provided in such digital cameras to supply light of an amount required for shooting at night.
A strobo which employs a xenon tube as a light emitting element is used as a flash in a general camera. The xenon tube emits light by being supplied with power previously charged on a main capacitor in response to a trigger signal. On the other hand, the charging of the main capacitor is performed just after the camera is powered on or after the strobo emits light, and requires a standby time of several seconds. For this reason, the strobo employing the xenon tube is disadvantageous in that the photographing cannot be performed for the standby time. Further, since the main capacitor is large in size, it is hard to apply the strobo employing the xenon tube to a small-size unit such as a mobile communication terminal.
Recently, an LED has been spotlighted as a light source replacing the xenon tube with the above problems. This LED is advantageous in that it requires no standby time, and is appropriate for miniaturization of an associated unit since it needs no large-size main capacitor.
An LED for a conventional camera flash is driven in such a manner that it continuously emits light of an amount necessary for photographing. That is, the LED continuously supplies light of an amount necessary for photographing even while a user determines a composition of a picture to be photographed. For this reason, for photographing in a very dark environment, high current must be continuously supplied to the LED in order to secure a desired amount of light for the photographing. In such a conventional LED drive system, an LED may continuously supply light of an amount desired for an image capture moment, resulting in an increase in current consumption. Moreover, current which is higher than rated current of the LED may be continuously supplied to the LED in order to secure the desired amount of light.
This conventional LED drive system has the disadvantage of significantly reducing the lifetime of a battery, particularly in a camera of a mobile communication terminal, due to unnecessary current consumption, and adversely affecting reliability of the LED due to the continuous supply of excessive current to the LED.